CVE-2026-92503 (GCVE-0-2026-92503)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:10 – Updated: 2026-09-17 16:10
VLAI
Title
ext4: fix ABBA deadlock in ext4_xattr_inode_cache_find()
Summary
In the Linux kernel, the following vulnerability has been resolved: ext4: fix ABBA deadlock in ext4_xattr_inode_cache_find() Syzbot/stress-ng reported an ABBA deadlock in ext4 when exercising concurrent xattr workloads (using the ea_inode mount/format option). The deadlock occurs between the running transaction and the eviction thread: - Task 1 (stress-ng): Holds a reference to a shared mbcache_entry (ce) and calls ext4_xattr_inode_cache_find() -> ext4_iget() to retrieve the corresponding EA inode. Since the EA inode is currently being evicted, ext4_iget() blocks in __wait_on_freeing_inode() waiting for eviction to complete. - Task 2 (eviction thread): Currently evicting the same EA inode in ext4_evict_ea_inode(). It calls mb_cache_entry_wait_unused(oe) which blocks waiting for Task 1 to release the reference to the mbcache_entry. To break this deadlock, implement a new ext4_iget() configuration flag named EXT4_IGET_NOWAIT. When set, perform a non-blocking lookup of the inode via VFS's find_inode_nowait() API. If the inode is currently being evicted (marked with I_FREEING or I_WILL_FREE) or created (I_CREATING), or if it is not present in the VFS inode cache (cache miss), simply skip it (returning -ENOENT) rather than waiting for eviction/creation to complete, breaking the ABBA cycle. Since we return -ENOENT immediately on a cache miss, we never attempt to allocate a new inode or call iget_locked(), completely eliminating any TOCTOU race window. If the returned inode is I_NEW, wait for its initialization to clear via wait_on_new_inode(). If initialization fails and the inode is unhashed during wait_on_new_inode() waking up (e.g., due to an I/O read error in another thread), safely drop the reference and return -ENOENT. This unhashed check is executed unconditionally on all cache-hit pathways to properly handle concurrent initialization failures. Finally, standard validation checks (including is_bad_inode, EXT4_EA_INODE_FL, file_acl, and xattr flags) are executed as normal inside check_igot_inode() to fully guarantee VFS-layer safety. In ext4_xattr_inode_cache_find(), invoke ext4_iget() with the new EXT4_IGET_NOWAIT flag to perform the non-blocking cache search.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 0a46ef234756dca04623b7591e8ebb3440622f0b , < 7720fddd1fe344d14be258a2028f74ebf1569511 (git)
Affected: 0a46ef234756dca04623b7591e8ebb3440622f0b , < 03438084a7b8621fb5c762dd3d04cff5f2630fb2 (git)
Affected: 0752e7fb549d90c33b4d4186f11cfd25a556d1dd (git)
Affected: 737fb7853acd5bc8984f6f42e4bfba3334be8ae1 (git)
Affected: 111103907234bffd0a34fba070ad9367de058752 (git)
Affected: 6.1.107 , < 6.2 (semver)
Affected: 6.6.47 , < 6.7 (semver)
Affected: 6.9.7 , < 6.10 (semver)
guessed Create a notification for this product.
Linux Linux Affected: 6.10
Unaffected: 0 , < 6.10 (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ext4/ext4.h",
            "fs/ext4/inode.c",
            "fs/ext4/xattr.c"
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          "versions": [
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              "versionType": "git"
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              "versionType": "semver"
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              "version": "6.9.7",
              "versionType": "semver"
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          "product": "Linux",
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            "fs/ext4/ext4.h",
            "fs/ext4/inode.c",
            "fs/ext4/xattr.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "6.10"
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              "version": "0",
              "versionType": "semver"
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix ABBA deadlock in ext4_xattr_inode_cache_find()\n\nSyzbot/stress-ng reported an ABBA deadlock in ext4 when exercising\nconcurrent xattr workloads (using the ea_inode mount/format option).\n\nThe deadlock occurs between the running transaction and the eviction\nthread:\n- Task 1 (stress-ng): Holds a reference to a shared mbcache_entry (ce)\n  and calls ext4_xattr_inode_cache_find() -\u003e ext4_iget() to retrieve\n  the corresponding EA inode. Since the EA inode is currently being\n  evicted, ext4_iget() blocks in __wait_on_freeing_inode() waiting for\n  eviction to complete.\n- Task 2 (eviction thread): Currently evicting the same EA inode in\n  ext4_evict_ea_inode(). It calls mb_cache_entry_wait_unused(oe) which\n  blocks waiting for Task 1 to release the reference to the mbcache_entry.\n\nTo break this deadlock, implement a new ext4_iget() configuration flag\nnamed EXT4_IGET_NOWAIT. When set, perform a non-blocking lookup of the\ninode via VFS\u0027s find_inode_nowait() API.\n\nIf the inode is currently being evicted (marked with I_FREEING or\nI_WILL_FREE) or created (I_CREATING), or if it is not present in the VFS\ninode cache (cache miss), simply skip it (returning -ENOENT) rather than\nwaiting for eviction/creation to complete, breaking the ABBA cycle.\n\nSince we return -ENOENT immediately on a cache miss, we never attempt to\nallocate a new inode or call iget_locked(), completely eliminating any\nTOCTOU race window.\n\nIf the returned inode is I_NEW, wait for its initialization to clear via\nwait_on_new_inode(). If initialization fails and the inode is unhashed\nduring wait_on_new_inode() waking up (e.g., due to an I/O read error in\nanother thread), safely drop the reference and return -ENOENT. This\nunhashed check is executed unconditionally on all cache-hit pathways to\nproperly handle concurrent initialization failures.\n\nFinally, standard validation checks (including is_bad_inode,\nEXT4_EA_INODE_FL, file_acl, and xattr flags) are executed as normal inside\ncheck_igot_inode() to fully guarantee VFS-layer safety.\n\nIn ext4_xattr_inode_cache_find(), invoke ext4_iget() with the new\nEXT4_IGET_NOWAIT flag to perform the non-blocking cache search."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-17T16:10:16.062Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/7720fddd1fe344d14be258a2028f74ebf1569511"
        },
        {
          "url": "https://git.kernel.org/stable/c/03438084a7b8621fb5c762dd3d04cff5f2630fb2"
        }
      ],
      "title": "ext4: fix ABBA deadlock in ext4_xattr_inode_cache_find()",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-92503",
    "datePublished": "2026-09-17T16:10:16.062Z",
    "dateReserved": "2026-09-16T12:21:13.872Z",
    "dateUpdated": "2026-09-17T16:10:16.062Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-09-30",
      "epss": "0.00198",
      "percentile": "0.08592"
    },
    "microsoft_vex": {
      "current_release_date": "2026-09-23T02:33:58.000Z",
      "cve": "CVE-2026-92503",
      "id": "msrc_CVE-2026-92503",
      "initial_release_date": "2026-09-19T01:20:35.000Z",
      "product_status:known_affected": "2",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "ext4: fix ABBA deadlock in ext4_xattr_inode_cache_find()",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-92503.json",
      "version": "2"
    },
    "nvd": {
      "cve": {
        "affected": [
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            "affectedData": [
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                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
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                  "fs/ext4/inode.c",
                  "fs/ext4/xattr.c"
                ],
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                "vendor": "Linux",
                "versions": [
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix ABBA deadlock in ext4_xattr_inode_cache_find()\n\nSyzbot/stress-ng reported an ABBA deadlock in ext4 when exercising\nconcurrent xattr workloads (using the ea_inode mount/format option).\n\nThe deadlock occurs between the running transaction and the eviction\nthread:\n- Task 1 (stress-ng): Holds a reference to a shared mbcache_entry (ce)\n  and calls ext4_xattr_inode_cache_find() -\u003e ext4_iget() to retrieve\n  the corresponding EA inode. Since the EA inode is currently being\n  evicted, ext4_iget() blocks in __wait_on_freeing_inode() waiting for\n  eviction to complete.\n- Task 2 (eviction thread): Currently evicting the same EA inode in\n  ext4_evict_ea_inode(). It calls mb_cache_entry_wait_unused(oe) which\n  blocks waiting for Task 1 to release the reference to the mbcache_entry.\n\nTo break this deadlock, implement a new ext4_iget() configuration flag\nnamed EXT4_IGET_NOWAIT. When set, perform a non-blocking lookup of the\ninode via VFS\u0027s find_inode_nowait() API.\n\nIf the inode is currently being evicted (marked with I_FREEING or\nI_WILL_FREE) or created (I_CREATING), or if it is not present in the VFS\ninode cache (cache miss), simply skip it (returning -ENOENT) rather than\nwaiting for eviction/creation to complete, breaking the ABBA cycle.\n\nSince we return -ENOENT immediately on a cache miss, we never attempt to\nallocate a new inode or call iget_locked(), completely eliminating any\nTOCTOU race window.\n\nIf the returned inode is I_NEW, wait for its initialization to clear via\nwait_on_new_inode(). If initialization fails and the inode is unhashed\nduring wait_on_new_inode() waking up (e.g., due to an I/O read error in\nanother thread), safely drop the reference and return -ENOENT. This\nunhashed check is executed unconditionally on all cache-hit pathways to\nproperly handle concurrent initialization failures.\n\nFinally, standard validation checks (including is_bad_inode,\nEXT4_EA_INODE_FL, file_acl, and xattr flags) are executed as normal inside\ncheck_igot_inode() to fully guarantee VFS-layer safety.\n\nIn ext4_xattr_inode_cache_find(), invoke ext4_iget() with the new\nEXT4_IGET_NOWAIT flag to perform the non-blocking cache search."
          }
        ],
        "id": "CVE-2026-92503",
        "lastModified": "2026-09-17T17:17:52.820",
        "metrics": {},
        "published": "2026-09-17T17:17:52.820",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/03438084a7b8621fb5c762dd3d04cff5f2630fb2"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/7720fddd1fe344d14be258a2028f74ebf1569511"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-23T16:58:42Z",
      "cve": "CVE-2026-92503",
      "id": "CVE-2026-92503",
      "initial_release_date": "2026-09-18T00:13:34Z",
      "product_status:known_affected": "162",
      "product_status:known_not_affected": "185",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-92503",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-92503.json",
      "version": "4"
    }
  }
}



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